The invention relates to the art of applying a coating compound to a web of fabric traveling through a coating machine. In particular, the invention relates to a type of coating machine which has a coating blade vertically arranged over a roller or other web support surface over which the web travels. A trough carried adjacent the coating blade supports a coating compound above the web of fabric. The trough and the coating blade are spaced apart to create a metering gap through which the coating compound is applied to the web.
One of the parameters for controlling the characteristics of the coating on the web is the amount of time that the coating compound remains on the fabric and is allowed to absorb before contacting the coating blade. This parameter is commonly referred to as the absorption rate of the coating compound. The absorption rate is directly proportional to the amount of time that the coating compound is allowed to stand over the area of the fabric prior to reaching the coating blade. In order to control the absorption rate, the width of the metering gap can be adjusted to narrow or widen the width of the coating compound on the fabric. If the metering gap is set wider, the coating compound will be allowed to stand on the fabric for a longer period of time prior to contacting the coating blade. In this instance, the coating compound will have a high absorption rate. In order to control the coating characteristic of the fabric, it is desirable to adjust the metering gap while the web is traveling through the coating machine.
The problem occurs that the metering gap in the prior coating machines cannot be readily adjusted while the web is traveling through the machine. One reason is that the trough of the coating machine normally includes a pair of laterally spaced sealing dams. The sealing dams contain the coating compound to the width of the web traveling through the machine. Excess coating compound at the fabric edges is reduced.
Sensors, such as electric eyes, are utilized to sense the edges of the fabric and adjust the lateral position of the sealing dams to follow the fabric edges. While the sealing dams are adjustable in the lateral position, no sealing dams have been heretofore provided which are adjustable in a longitudinal direction in which the web travels through the coating machine. To adjust the longitudinal position of the trough relative to the coating blade to vary the metering gap width has required that the coating machine be stopped. With the coating machine stopped, the trough is set in a desired position to provide a desired metering gap. The sealing dams are removed and interchanged with additional sealing strips or material placed around the dams in an effort to seal the dams in a different trough position which has not been entirely satisfactory. All of the foregoing takes considerable time and effort on behalf of the machine operator. Furthermore, while the machine is stopped, the coating compound is deposited on the web and absorbed in an uncontrolled fashion. This leaves a portion of the fabric having too much coating.
Laterally adjustable sealing dams for controlling the width of glue and the like applied to a roll are shown in U.S. Pat. Nos. 4,338,881, 4,327,662, and 3,936,549. However the foregoing are not adjustable in the direction of web travel nor suitable for adjusting to trough position in a trough over fabric feed system.
Accordingly, an important object of the present invention is to provide an apparatus and method for adjusting the width of the metering gap on a coating machine while a web of fabric is traveling through the coating machine.
Still another important object of the present invention is to provide adjustable sealing dams for containing the width of a coating compound on a coating machine wherein the sealing dams adjust longitudinally to automatically compensate for changes in a trough position to vary a metering gap on the coating machine.
Still another important object of the present invention is to provide an adjustable sealing dam for use in a coating trough of a coating machine which automatically adjusts to the longitudinal movement of the trough to maintain a fluid type dam on each end of a coating compound in the trough while the trough prevents the weight of the compound from sitting directly on the fabric to thereby control absorption into the fabric.
Still another important object of the present invention is to provide a sealng dam for a trough of a coating machine which is adjustable both laterally and longitudinally in the trough, yet is simple in construction, and is reliable during both movements in maintaining a fluid type seal of the coating compound.